1. Field of the Invention
The present invention relates to a direct current linear motor variously used for precisely moving an object to be moved in a linear motion mechanism such as a machine tool or industrial robot, and a direct drive unit in which a guiding device for guiding said object is added to said direct current linear motor.
2. Description of the Prior Art
An example of this type of direct current linear motor and direct drive unit of the prior art is the movable magnet type indicated in FIG. 1. Furthermore, an example of this prior art is disclosed in Japanese Examined Utility Model Publication 63-34468.
As indicated in FIG. 1, said direct current linear motor has a primary side comprising coil yoke 2 provided so as to extend along roughly the entire length (with the lengthwise direction being the direction perpendicular to the paper surface) of long guide rail 1 on said guide rail, and armature coil group 3 wound in a prescribed form on said coil yoke 2. In contrast, the secondary side has field magnet 5 mounted so that a plurality of N and S magnetic poles are alternately arranged along the lengthwise direction of guide rail 1 in the direction of movement, and magnet yoke 6 provided behind said field magnet 5. These primary and secondary sides are arranged so that the respective armature coil group 3 and field magnet 5 are mutually opposing each other while allowing relative movement. More specifically, a pair of rollers 7a and 7b are provided on both sides of magnet yoke 6 mounted on field magnet 5. Each of said rollers is able to roll on guide rail 1. A guiding device that mutually guides the above-mentioned primary and secondary sides is composed by these rollers 7a,7b and guide rail 1.
Printed board 8 is attached on the bottom surface of coil yoke 2. Electronic component group 9, including IC and transistors that compose a control circuit, is attached on the bottom surface of this printed board 8. In addition, electromagnetic conversion device 10, comprising a Hall device for detecting the relative positions of the above-mentioned primary and secondary sides, is mounted on the upper side of printed board 8. A plurality of these electromagnetic conversion devices 10 are mounted in a row at prescribed pitch in the direction of relative movement of the above-mentioned primary and secondary sides, and oppose field magnet 5 through opening 2a formed in coil yoke 2.
In the direct drive unit containing the direct current linear motor having the above-mentioned constitution, thrust is produced in accordance with Fleming's left hand rule between the primary and secondary sides as a result of supplying a prescribed electrical current to armature coil group 3. If, for example, the primary side is taken to be the stationary side, the secondary side moves due to this thrust.
The above-mentioned direct current linear motor and direct drive unit of the prior art has the disadvantage of printed board 8, equipped with electromagnetic conversion device 10 and a control circuit including electronic component group 9, and coil yoke 2, that is a constituent member of the primary side, taking up a comparatively large amount of space. As such, this disadvantage must be overcome in order to reduce the overall size and thickness of said motor and unit. In addition, the large number of parts contributes to increased costs.
Moreover, since printed board 8 is heat insulated, heat produced by the IC and transistors, etc., provided on said printed board tends to accumulate easily, thus resulting in the risk of this heat having a detrimental effect on the control circuit.